Barometer problem.

Still talking about hydrostatic pressure.

Yes, I am not done with hydrostatic pressure yet!

One of the problems students were given in the study “Identifying and addressing student difficulties with hydrostatic pressure” by Loverude, Heron and Kautz is a barometer problem.

hydrostaticpressure02
Barometer problem – compare the pressure at point x and y.

Students are asked to compare the pressure at point X and point Y. Apparently, this is not as obvious as it seems to me. So before I go into the detailed discussion (I might do it in a later post – anyone interested in reading it?), I thought I’d just set this up. Because to me it seems that if you see this sitting there with the liquid clearly not moving one way or another, the solution has to be clear. We’ll see what others think, but here we go:

If you want proof that the tubes are open at the bottom and that there still is a hydrostatic equilibrium, watch the movie below. Spoiler alert: You might have fallen asleep by the time things start moving in the movie ;-)

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